The availability of RC 1 really surprised me. The Netbeans 6.0b2 is just few weeks old and now the RC1 is already available. The Netbeans 6.0b2 worked fine for me (I'm working in Java EE/Swing area now), however I had sometimes problems with the generation of "JMS-Sender" code. I switched yesterday to RC1 and the problems are gone. The IDE feels faster as well - however it is hard to quantify this impression.
Reading the release notes I found an interesting link to a bunch of really useful screencasts (Web, Swing, Profiler, Restful services).
I installed some plugins and I like the Plugin-manager very much. Instead of pointing to random URLs, you can easily search for interesting plugins without knowing where they actually are. Some of the plugins can be even installed without restarting the IDE.
However there is one thing - which I really hate: If you create an Entity Class - Netbeans annotates the methods, and not the fields, which is an absolute anti-pattern. This changed in b1 or b2 - but worked fine in 5.5.1.
The explorer (Projects Tab) could be optimized for Java EE projects as well. E.g. ejb-jars, wars, appclients could be displayed inside the ear. Now although the modules actually reside inside the EAR, they appear on the same level - it's harder to find the module in case you have many projects open (in my case about 50...).
However it is really fun to work with netbeans and track the improvements from version to version (even from daily build to daily build). The pace is unbelievable. One of my favourites is the Java FX plugin. It already supports syntax highlighting, outline view, error annotations and preview. It works really well. If you would like to learn more about JavaFX - just create the Weather Example in Netbeans it shows some interesting concepts like: interaction with Java Classes, asynchronous XML loading, binding and animations -> well done.
I'm curious whether the code completion will be available as well for Java FX Script....
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